1. Field of the Invention
This invention relates to an improvement in sign structures wherein the sign face is formed on a sheet of film and in one aspect to a sign housing that is designed to balance the pressure on the rear surface of the sign face with the wind pressure on the exposed front face of the film to maintain a static balance of the film.
2. Description of the Prior Art
Signs having a housing with an open front face in which is positioned a sign face which may be permanent or changeable are well known. The sign face in most of these structures is rigid plastic material or glass and is backlighted for illuminating the sign. It is also known in the prior art to suspend sheet material from its corners to provide a large sign board or to place a film over the front of the housing.
The disadvantages of the rigid plastics (such as acrylics, polycarbonates, cellulose acetate butyrate materials, fiberglass, etc.) for illuminated signs is that the use of such materials is cumbersome and expensive for large outdoor advertising purposes. It is difficult and costly to change the heavy sign faces. The weight requires heavy structural members in the frame and extensive lifting mechanisms. Additionally, the rigid sheets are subject to breakage from sudden wind gusting and from vandalism.
The suspended flexible sheet material is subject to bowing when receiving a wind force and when a high wind loading occurs the material will tear or become twisted.
A flexible plastic sheet adhered over an opening in a housing will bow and may strike the lamps or other structure within the sign or it will receive such a force that the plastic film will suffer permanent distortion because of the high wind loading against the face of the sign.